Cultured human endothelial cells synthesize a plasma membrane protein complex immunologically related to the platelet glycoprotein IIb/IIIa complex

We have previously demonstrated that endothelial cells synthesize a plasma membrane protein indistinguishable from platelet glycoprotein (GP) IIa. The present study provides evidence for a further analogy between the platelet and the endothelial cell membrane by showing that cultured endothelial cells also synthesize a membrane protein complex immunologically related to the platelet GP IIb/GP IIIa complex. This evidence is based on the following observations: (1) C17, a murine monoclonal antiplatelet GP IIIa antibody, consistently precipitates two proteins, apparent molecular weights, respectively, 115,000 and 125,000 reduced and 95,000 and 135,000 nonreduced, from metabolically (35S- methionine) as well as surface 125I-labeled cultured human endothelial cells; (2) upon crossed immunoelectrophoresis of solubilized endothelial cells against a polyclonal rabbit antiplatelet antiserum and 125I-labeled C17 IgG, a single precipitate of the protein(s) recognized by C17 is observed. As judged by their mobility in 9% polyacrylamide gels, both endothelial proteins appear to have a somewhat larger molecular weight than their platelet counterparts. Patterns obtained by crossed immunoelectrophoresis are also indicative of a difference in electrophoretic behavior of the platelet GP IIb/IIIa complex and the endothelial cell protein complex.     

No evidence for a prethrombotic state in stable chronic inflammatory bowel disease

Ulcerative colitis and Crohn's disease are associated with a high risk of thromboembolic complications. The questions whether reported risk factors such as low antithrombin III concentrations, thrombocytosis and spontaneous platelet aggregation are merely related to the activity of the inflammatory process remains to be answered. Therefore we investigated 40 patients with an established colitis or Crohn's disease, without signs of active inflammation (normal history, normal ESR and leucocyte count). Of these patients only one patient revealed thrombocytosis, six patients spontaneous platelet aggregation. All patients had normal beta-thromboglobulin and platelet factor 4 plasma levels. No other prethrombotic abnormalities were encountered. There was normal factor VIII C (increased in three patients), normal VIII C/VIII R Ag ratio (1.2), antithrombin III, normal plasminogen and normal alpha 2-antiplasmin. Normal fibrinopeptide A and B beta (15-42) plasma levels (n = 15) in these patients excluded in vivo thrombin or plasmin generation. We conclude that stable chronic inflammatory bowel disease is in general not associated with prethrombotic coagulation abnormalities.     

Reactive hemophagocytic syndrome as a presenting feature of Hodgkin's disease

We report the case of a 60-year-old man with febris of unknown origin, severe pancytopenia, and rapidly developing splenomegaly due to reactive hemophagocytic syndrome and Hodgkin's disease. Reactive hemophagocytic syndrome is often rapidly fatal and, once this diagnosis is considered, an underlying infection or malignancy should be treated promptly. An extensive search of the literature revealed only two other cases of reactive hemophagocytic syndrome and Hodgkin's disease. This is the only reported patient who survived after being diagnosed as having reactive hemophagocytic syndrome and Hodgkin's disease. Received: 12 October 1998 / Accepted: 4 November 1999     

Monoclonal antibodies against human platelet glycoprotein IIIa

Two murine monoclonal antibodies specific for human platelets were prepared and characterized by immunofluorescence, immunoprecipitation and by studying their effect on platelet function. Immunoprecipitation with lysates of normal platelets and platelets from a patient with Glanzmann's thrombasthenia revealed that the monoclonal antibodies were directed against glycoprotein GP IIIa. One of these anti-GP-IIIa antibodies (C17) inhibited both ADP- and collagen-induced platelet aggregation as well as ADP-induced fibrinogen binding to platelets. The other anti-GP-IIIa antibody (C15) also caused a complete inhibition of aggregation with collagen. However, a small, and fully reversible, 'primary wave' was observed if the platelets were stimulated with ADP when platelet-rich plasma was used. The ability to bind fibrinogen was unimpaired for platelets incubated with C15. These findings show that C15 and C17 probably recognize different determinants on GP IIIa. Neither of the monoclonal anti-GP-IIIa antibodies blocked the binding to Zwa-positive platelets of human polyclonal anti-Zwa antibodies. This implies that Zwa is different from the epitopes recognized by C15 and C17.